Rotary switch with indexing mechanism



March 3, 1970 cK ET AL 3,499,133

ROTARY SWITCH WITH INDEXING MECHANISM Filed April 11, 1968 2Sheets-Sheet l INVENTQRS. ROBERT/I. TILLACK BY ALLAN J. SV/(ORA ATTORNEY9 March 3, 1970 H, TILLACK ET AL 3,499,133

ROTARY SWITCH WITH INDEXING MECHANISM Filed April 11, 1968 2Sheets-Sheet 2 JNVENTORS. 'Q BEAT H. r/LLAcW ALLAN .1. swram ATTORNEKS.

Patent 3,499,133 ROTARY SWITCH WITH INDEXING MECHANISM Robert H.Tillack, Raleigh, and Allan J. Sykora, Cary, N.C., assignors toStackpole Carbon Company, St. Marys, Pa., a corporation of PennsylvaniaFiled Apr. 11, 1968, Ser. No. 720,601 Int. Cl. H01h 3/00, 9/00 US. Cl.200166 6 Claims ABSTRACT OF THE DISCLOSURE It is among the objects ofthis invention to provide a rotary switch, which includes an indexingmechanism of inexpensive construction having a long life, asubstantially constant torque, and means for automatically compensatingfor wear.

In accordance with this invention, the front wall of a rotary switchhousing is provided with a central opening in which a shaft is rotatablymounted. A movable contact carried by the inner end of the shaft isengageable, when the shaft is turned, with fixed contacts mounted in thehousing. Rigidly mounted on the shaft between the movable contact andthe front wall of the housing is an index plate that is provided withcircumferentially spaced indexing recesses. Slidably mounted on theshaft between the index plate and the front wall is a pressure platespaced from the index plate and provided with at least one ear thatprojects laterally into a radial slot, with which the inside of thehousing is provided. Preferably, there are two or more of these ears andslots. The slots extend lengthwise of the housing and have open rearends. A ball is disposed in each slot between the ear therein and theindex plate. Compressed between the front wall of the housing and thepressure plate there is a coil spring that causes the ears to press theballs into the adjoining index plate recesses. Consequently, when theindex plate is turned by the shaft, the portions of that plate betweenadjacent indexing recesses will push the balls toward the front wall ofthe housing until the balls are received in the next recesses.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which FIG. 1 is a front view of the switch;

FIG. 2 is a side view thereof;

FIG. 3 is an enlarged longitudinal section taken on the line IIIIII ofFIG. 1;

FIG. 4 is an enlarged longitudinal section taken on the line IV1V ofFIG. 2;

FIG. 5 is a cross section taken on the line VV of FIG. 3; and

FIGS. 6 and 7 are enlarged cross sections taken on the lines VI-VI andVIIVII, respectively, of FIG. 2.

Referring to the drawings, the switch may be any type of rotary switchin which a movable contact carried by a rotatable shaft is moved intoand out of engagement with fixed contacts by turning the shaft. For thepurpose of illustration only, the switch that is shown is similar to theone disclosed in Patent 3,258,547. Thus, a switch housing 1 has frontand rear end walls connected by a side wall. The inside of the housingis a 3,499,133- Patented Mar. 3, 1970 ice cylindrical chamber 2. Thehousing shown is made from four parts. The front part of the housing isa cup-like member 3, while the back part of the housing is formed fromtwo rings 4 and 5 of plastic and a separate end wall 6. These four partsare rigidly secured together by rivets 7 extending through perforatedbosses 8 projecting from their outer surfaces at diametrically oppositepoints. Another ring can be added, if desired, without changing thelength of the rivets by simply removing material from the front ends ofthe bosses on front member 3.

Molded in one of the plastic rings is a metal ring that projects intothe housing chamber to form an annular collector 11 as shown in FIG. 6.Integral with this ring and projecting out of the housing from it is aterminal 12. Molded in the other plastic ring, as shown in FIG. 7, arethe central portions of a plurality of circumferentially spaced metalstrips that project into the housing chamber to form uniformly spacedfixed contacts 13. The strips also project radially from the ring toform electrical terminals 14. The fixed contacts can be spaced fartherapart if desired, without interfering with smooth operation of theswitch, if metal tabs 15 are molded into the ring between the contactsto partially span the space between them.

Rigidly mounted in a central opening 17 in the front wall of the housingis a bushing 18 that extends in both directions from the opening. Theouter end portion of the bushing is threaded so that the switch can bemounted on a panel in the customary manner by inserting the bushing inan opening in the panel and then screwing a nut on the bushing.Rotatably mounted in the bushing is a shaft 19 that extends through thehousing to a point near its rear end wall 6. The outer end of the shaftlikewise projects from the bushing and is adapted to receive a knob forturning it. If movement of the shaft into the housing is not intended tobe limited by the rear wall of the housing, it can be limited by a stopring 20 mounted in a circumferential groove in the shaft and engagingthe outer end of the bushing.

To connect the annular collector 11 with any fixed contact, aninsulating rotor disc 22 is mounted on the flattened inner end portionof the shaft for rotation by the shaft. The rotor extends radiallyoutward between the collector and the fixed contacts but it is spacedfrom both. As shown in FIG. 3, this rotor is provided with one or moreopenings 23 through it near its periphery, with at least the outer endportions of the openings located between the collector and the fixedcontacts. Dis-- posed in at least one of these openings is a movablecontact 24 that bridges the space between the collector and the fixedcontacts. The movable contact preferably is a generally U-shaped tinystrip of spring metal, the spaced outer ends of which engage thecollector and one of the fixed contacts. When the shaft is rotated, themovable contact or contacts will be carried around the inside of thehousing from one fixed contact to another.

It is a feature of this invention that the switch includes an indexingmechanism so that the movable contact can be held against any fixedcontact desired without moving away from its until the shaft is turnedmanually. Accordingly, an index plate 26 is rigidly mounted on the shaftat the rear end of the front member 3 of the housing a short distanceaway from the fixed contacts. The plate also is spaced from the innerend of the bushing. This plate is provided with aplurality ofcircumferentially spaced indexing recesses 27. There are as manyrecesses as there are fixed contacts. Although these recesses could takethe form of small openings in the index plate, it is preferred to formthem by bending the marginal portion of the plate toward the front wallof the housing at circumferentially spaced intervals to produce spacedprojections 28 that form the sides of the recesses. The bendingoperation is such that it gives the edge of the index plate a scallopedappearance as shown in FIG. 4 so that the recesses are concave and theends of projections 28 are convex.

Between the index plate and the inner end of the bushing, and spacedfrom both, there is a pressure plate 30 that is slidably mounted on theshaft. This plate has a central body parallel to the index plate andcircumferentially spaced, laterally projecting cars 31. Twodiametrically opposite ears are sufficient as shown in FIG. 5. For bestresults, the ears are integrally connected to the central body byportions 32 of the pressure plate that extend from the body toward thefront end of the housing substantially parallel to the shaft. Theseconnecting portions may be about the same width as the ears themselves.The ears project into a pair of radial slots 33, with which the insideof the front member of the housing is provided. These slots extendlengthwise of the housing and have open rear ends. The ears fit looselyenough in the slots to permit the ears to move freely lengthwise of theslots. Disposed in each slot between the ear and the index plate is ametal ball 34 that engages the side walls of the slot. Connectingportions 32 of the pressure plate help to hold the balls in the slots,especially while the switch is being assembled.

A coil spring 36 encircles the shaft between the front wall of thehousing and pressure plate 30. The spring is under compression andtherefore it urges the pressure plate toward the index plate, so ears 31press the balls into two of the index plate recesses 27 to prevent theindex plate and shaft from turning unless sufiicient torque is appliedmanually to the outer end of the shaft to turn it. When that happens,projections 28 on the index plate ride over the balls, pushing themtoward the front ends of the housing slots, which is permitted becausethe coil spring will compress further. As soon as the projections passthe balls, the spring will force the balls back into the next pair ofindexing recesses. In this way the movable contact can be indexed intoany desired position to electrically connect the collector with any ofthe fixed contacts. In some cases it may be desirable to use only asingle ball. In such a case it is desirable to insert a spacing washerbetween the index plate and the pressure plate to prevent the latterfrom tilting excessively when the ball is in a recess 27.

Another feature of this invention is that wear of the balls or the sidewalls of the slots containing them is automatically compensated for bytapering the slots radially outward in cross section as shown in FIG.and by having the ears 31 diverge toward the front end of the housing sothat they are inclined to the axis of the shaft. The inclined earstherefore urge the balls radially outward in the slots so that the ballsalways remain in engagement with both side walls of each slot eventhough the slots may become wider during use, or the balls becomesmaller.

The indexing mechanism disclosed herein has a long life compared toother rotary switch indexing mechanisms. Due to the use of a coilspring, a greater torque range can be provided than with conventionalflat springs, and no appreciable change in torque is evident over theextended life of the indexing mechanism. The use of two balls provides abalanced, positive, detent action. The front member of the switchhousing can be a metal die casting which permits it to be grounded ifdesired, or it can be molded from a plastic, which of course willinsulate it from grounding.

We claim:

1. A rotary switch comprising a housing having front and rear end walls,the front wall provided with a central opening therethrough, a shaftrotatably mounted in said opening, means limiting axial movement of theshaft rearwardly into the housing, a movable contact carried by theinner end of the shaft, fixed contacts mounted in the housing forengagement by said movable contact when the shaft is turned, an indexplate rigidly mounted on the shaft between the movable contact and saidfront wall and provided with a plurality of circumferentially spacedindexing recesses, a pressure plate slidably mounted on the shaftbetween the index plate and said front wall, the pressure plate spacedfrom the index plate and provided with a laterally projecting ear, theinside of the housing provided with a radial slot extending lengthwiseof the housing for receiving said ear and having an open rear end, aball disposed in said slot between the ear therein and the index plate,and a spring in the housing urging the pressure plate toward the indexplate to cause said ear to press the ball into the adjoining index platerecess, whereby when the index plate is turned by the shaft the portionsof that plate between adjacent indexing recesses will push the balltoward said front wall until the ball is received in the next recess.

2. A rotary switch according to claim 1, in which said index platerecesses are formed between circumferentially spaced peripheral portionsof the index plate projecting toward said front wall of the housing.

3. A rotary switch according to claim 1, in which said ear isinclinedtoward said front wall, said slot tapers radially outward, and the ballengages the opposite side walls of the slot containing it.

4. A rotary switch according to claim 1, in which said pressure platehas a central body substantially parallel to the index plate, and saidear is integrally connected to said body by a portion of the pressureplate that extends from said body toward said front wall and issubstantially parallel to the shaft.

5. A rotary switch according to claim 4, in which said ear is inclinedtoward said front wall, said slot tapers radially outward, and the ballengages the opposite side walls of the slot containing it.

6. A rotary switch according to claim 1, including a plurality of saidears circumferentially spaced around the pressure plate, a plurality ofsaid slots receiving said ears, and a ball in each slot.

References Cited UNITED STATES PATENTS 2,845,501 7/ 1958 George.3,189,695 6/1965 Randolph. 3,258,547 6/1966 Rector. 3,336,816 8/1967Medicks et al. 3,363,068 1/1968 Schwab.

HERMAN O. JONES, Primary Examiner US. Cl. X.R' 200-11

